A terrified couple have told how an egg hurled from a motorway bridge near Cambridge could have “caused carnage” after it cracked the wing mirror of their car.

Dan Smith, 24, of Moat Way, Swavesey, and his wife Jessica, 26, an Addenbrooke’s Hospital nurse, were driving under the cycle bridge on the M11 just before the turnoff for Madingley Road when the attack happened.

The couple were travelling at about 70mph on the motorway when the egg smashed into their Audi Cambridgeshire police have now issued a warning to missile-throwers highlighting the dangers of the illegal activity.

Mr Smith, managing director of web designers PrimeXeon, said: “We heard what sounded like a rock. It was awful. We looked and t was an egg that had been thrown from the bridge. The gravity and the force of our car as we were doing about 70mph, was incredible.

“It cracked the wing mirror plastic surrounding it and made a right mess of my car. My wife called the police straight away and they did send some officers but as you would expect the kids that did this had already fled the scene.

“Luckily it only caused some minor damage to my car but I can’t believe to imagine the carnage if it hit my windscreen and it smashed it or it hit a motorcyclist and would then have been enough to knock them off the bike.

“I had just been to an Audi dealership to get a new car as part exchange for the one I was driving. Now I have to pay to get it fixed before I can get my new car.

“I just want to highlight to at least a few of these kids that think it’s a funny prank that it could very easily cause a fatality on the motorway.”

The terrifying incident happened at about 5.30pm on Saturday.

A police spokesman said: “We received a report that a wing mirror on an Audi A3 was cracked after an egg was thrown from a cycle bridge over the M11 at Madingley.

“Throwing objects at vehicles, especially when they are travelling at high speeds on motorways, is extremely dangerous and we take such offending very seriously.

“We would urge anyone with information to call police on 101.”

HOW DOES AN EGG CRACK A CAR? We ask a ‘Bouncing Bomb’ expert

A Dambusters expert at Cambridge University has explained how an egg could damage a car at high speed.

Dr Hugh Hunt, an expert in dynamics who was behind the award-winning TV documentary, Dambusters: Building The Bouncing Bomb, is a senior lecturer at the Department of Engineering.

He said: “The egg could have been going fast and combined with the speed of the car and the egg itself impacting could cause the damage.

“If you imagine diving into a swimming pool, the water is very soft but if you were to dive from a high cliff or at 70mph the water might as well be concrete.

“The egg hitting a car at speed would be the same thing. The egg may as well be concrete.”